AB0032 DIFFERENTIAL IMPACT OF BIOLOGICS AND GLUCOCORTICOIDS ON TNF SECRETION AND CD14+CD16+ MONOCYTES PERCENTAGE IN CULTURE DERIVED FROM SYNOVIAL FLUIDS OF PATIENTS WITH PSORIATIC ARTHRITIS-IN VITRO RESEARCH

Background:Inflammatory joint diseases, such as psoriatic arthritis (PsA), are frequently treated by biologics. Assessment of treatment efficacy is based upon change in clinical activity scores and in tender and swollen joint counts. Although the response to these agents may be attributed to their central anti-inflammatory effects, synovial response may be operating in parallel. The potential beneficial role of intra-articular injection of tumor necrosis factor (TNF) blockers compared to glucocorticoids (GCs) in reducing synovitis was shown by means of clinical and instrumental validated measures (1). The inflamed synovial fluid is rich in mononuclear cells, however, the different mode of action of the in vitro response of these cells to drugs may contribute to the understanding of cellular response to therapeutic agents in central as opposed to peripheral compartments.Objectives:To evaluate the effect of biologics used in the management of PsA on synovial fluid mononuclear cells (SFMCs) in vitro, and to compare their modes of action to GCs that are used to locally alleviate synovial inflammation.Methods:SFMCs were obtained from PsA patients (n=11) during therapeutic knee arthrocentesis. The cells were cultured in vitro for 7 days in the presence of biologics (adalimumab, infliximab, secukinumab and ustekinumab, 10ug/ml) and GCs (betamethasone and methylprednisolone, 1 ug/ml and 10ug/ml) or medium as control. Levels of the secreted TNF were measured by ELISA. Changes in %CD14+CD16+ monocytes were analyzed by flow cytometry.Results:Both TNF inhibitors (adalimumab p<0.01, infliximab p=0.0003) and GCs (betamethasone and methylprednisolone at 1ug/ml p<0.01 and at 10ug/ml p<0.04) significantly reduced TNF levels in cultured media derived from SFMCs of PsA patients (n=8) compared to medium. None of the other biologics reduced TNF levels in culture (Fig. 1A). Additionally, %CD14+CD16+ SFMCs derived from PsA patients (n=11) were significantly reduced by TNF inhibitors (p=0.0003) compared to medium, however, other biologics and GCs did not display similar activity (Fig. 1B).Figure 1.Both TNF inhibitors and GCs block TNF secretion but exhibit different activity on inflammatory CD14+CD16+ monocytes derived from SFMCs of PsA patients. SFMCs were co-cultured for 7 days in the presence of adalimumab, infliximab, secukinumab and ustekinumab at 10ug/ml or with betamethasone and methylprednisolone at 1ug/ml and 10ug/ml. Medium alone was used as a control. (A) Culture supernatants were analyzed for TNF levels by ELISA (n=8). (B) Cells were analyzed for %CD14+CD16+ monocytes by flow cytometry (n=11). All p values were calculated by the non-parametric one-way ANOVA Kruskal-Wallis test and Dunn’s multiple comparison test, *p<0.04, **p<0.01 and ***p=0.0003.Conclusion:Our data demonstrated marked activity mediated by TNF inhibitors in comparison with other biologics tested for their ability to suppress TNF secretion and inflammatory CD14+CD16+ monocytes. In contrast, GCs suppressed TNF secretion but did not significantly change the proportion of inflammatory CD14+CD16+ monocytes. These findings suggest an additional mechanism of action exerted directly by TNF inhibitors on synovial monocytes and which differs from that of GCs. These results warrant further studies of the therapeutic potential of local peripheral activity of TNF inhibitors for clinical application.Reference:[1]Carubbi F, Zugaro L, Cipriani P, Conchiglia A, Gregori L, Danniballe C, et al. Safety and efficacy of intra-articular anti-tumor necrosis factor alpha agents compared to corticosteroids in a treat-to-target strategy in patients with inflammatory arthritis and monoarthritis flare. Int J Immunopathol Pharmacol. 2016;29:252-66.Disclosure of Interests:None declared

Kupffer Cells Sense Free Fatty Acids and Regulate Hepatic Lipid Metabolism in High-Fat Diet and Inflammation

A high fat Western-style diet leads to hepatic steatosis that can progress to steatohepatitis and ultimately cirrhosis or liver cancer. The mechanism that leads to the development of steatosis upon nutritional overload is complex and only partially understood. Using click chemistry-based metabolic tracing and microscopy, we study the interaction between Kupffer cells and hepatocytes ex vivo. In the early phase of steatosis, hepatocytes alone do not display significant deviations in fatty acid metabolism. However, in co-cultures or supernatant transfer experiments, we show that tumor necrosis factor (TNF) secretion by Kupffer cells is necessary and sufficient to induce steatosis in hepatocytes, independent of the challenge of hepatocytes with elevated fatty acid levels. We further show that free fatty acid (FFA) or lipopolysaccharide are both able to trigger release of TNF from Kupffer cells. We conclude that Kupffer cells act as the primary sensor for both FFA overload and bacterial lipopolysaccharide, integrate these signals and transmit the information to the hepatocyte via TNF secretion. Hepatocytes react by alteration in lipid metabolism prominently leading to the accumulation of triacylglycerols (TAGs) in lipid droplets, a hallmark of steatosis.

Oral administration of EP4-selective agonist KAG-308 suppresses mouse knee osteoarthritis development through reduction of chondrocyte hypertrophy and TNF secretion

Osteoarthritis (OA) is one of the world’s most common degenerative diseases, but there is no disease-modifying treatment available. Previous studies have shown that prostaglandin E2 (PGE2) and PGE2 receptor 4 (EP4) are involved in OA pathogenesis; however, their roles are not fully understood. Here, we examined the efficacy of oral administration of KAG-308, an EP4-selective agonist, in surgically induced mouse knee OA. Cartilage degeneration and synovitis were significantly inhibited by the KAG-308 treatment. Chondrocyte hypertrophy and expression of tumor necrosis factor alpha (TNF) and matrix metalloproteinase 13 (Mmp13) in the synovium were suppressed in the KAG-308-treated mice. In cultured chondrocytes, hypertrophic differentiation was inhibited by KAG-308 and intranuclear translocation of histone deacetylase 4 (Hdac4) was enhanced. In cultured synoviocytes, lipopolysaccharide (LPS)-induced expression of TNF and Mmp13 was also suppressed by KAG-308. KAG-308 was detected in the synovium and cartilage of orally treated mice. TNF secretion from the synovia of KAG-308-treated mice was significantly lower than control mice. Thus, we conclude that oral administration of KAG-308 suppresses OA development through suppression of chondrocyte hypertrophy and synovitis. KAG-308 may be a potent candidate for OA drug development.

Anti-inflammatory activity of synthetic and natural glucoraphanin

Glucoraphanin is one of the best known glucosinolates because of its health benefits. The compound is known to eliminate carcinogens in tissue and hence is frequently studied for its cancer preventative properties. In this work, the total synthesis of ?- and ?-glucoraphanin epimers was attempted. ?-Glucoraphanin potassium salt was successfully synthesized in high overall yield, whereas the ?-epimer was found to be unstable as it decomposed in the final step of the total synthesis. The anti-inflammatory activity of the synthetic glucoraphanin was determined by inhibition of the release of tumor necrosis factor alpha (TNF-?) secretion in lipopolysaccharide-stimulated THP-1 cells. It was shown that in the presence of either the synthetic or natural glucoraphanin, TNF-? secretion was significantly reduced (?52 % inhibition) at a concentration of 15 ?M.

iTAP, a novel iRhom interactor, controls TNF secretion by policing the stability of iRhom/TACE

The apical inflammatory cytokine TNF regulates numerous important biological processes including inflammation and cell death, and drives inflammatory diseases. TNF secretion requires TACE (also called ADAM17), which cleaves TNF from its transmembrane tether. The trafficking of TACE to the cell surface, and stimulation of its proteolytic activity, depends on membrane proteins, called iRhoms. To delineate how the TNF/TACE/iRhom axis is regulated, we performed an immunoprecipitation/mass spectrometry screen to identify iRhom-binding proteins. This identified a novel protein, that we name iTAP (iRhom Tail-Associated Protein) that binds to iRhoms, enhancing the cell surface stability of iRhoms and TACE, preventing their degradation in lysosomes. Depleting iTAP in primary human macrophages profoundly impaired TNF production and tissues from iTAP KO mice exhibit a pronounced depletion in active TACE levels. Our work identifies iTAP as a physiological regulator of TNF signalling and a novel target for the control of inflammation.

TAK1ng control: TAK1 restrains NLRP3 activation

In this issue of JEM, Malireddi et al. (https://doi.org/10.1084/jem.20171922) demonstrate that macrophage-specific loss of TAK1 causes spontaneous NLRP3 inflammasome activation, driven by unregulated TNF secretion and signaling. This has implications for therapeutically targeting TAK1, enhancing its potential function as an anticancer drug treatment.